Abrasion resistant alloy steel

ABSTRACT

AN ABRASION-RESISTANT ALLOY STEEL CONTAINING MORE THAN 1.8% AND LESS THAN 2.5% MANGANESE AND LESSER PERCENTAGES OF NICKEL, MOLYBDENUM, COPPER, SILICON AND CARBON WHICH IS HEAT TREATED TO PROVIDE A HARDNESS OF AT LEAST 300 BHN AND IS WORK-HARDENABLE TO INCREASE THE INITIAL HARDNESS BY AT LEAST 15% TO PROVIDE A SUPERIOR ABRASION-RESISTANT ALLOY STEEL OF RELATIVELY LOW MANGANESE CONTENT WHOSE HARDNESS INCREASES IN USE.

United States Patent 3,761,320 ABRASlON-RESISTANT ALLOY STEEL Arthur Light, Shaker Heights, Ohio, assignor to Curtis Noll Corporation, Cleveland, Ohio No Drawing. Filed Mar. 6, 1972, Ser. No. 232,218 Int. Cl. C22c 39/30, 39/36 US. Cl. 148-3 3 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION There are many fields of use for a strong and tough alloy steel which has good abrasion resistance and impact resistance to provide long wear characteristics, particularly in the earth-moving and construction industries. To meet this need, the prior art has provided alloy steels having a relatively high manganese content in the range of 12-14% and also usually containing other alloy elements, such as molybdenum, from 15 %to 25%. Such high-manganese alloy steels have a fair abrasion resistance and a very good impact resistance, resulting primarily from the ability of such high-manganese alloy steels to harden under impact in field use.

Insofar as is known, the prior art has not developed any low cost alloy steel which will provide the desired abrasion resistance and impact resistance, without the high manganese content above noted.

SUMMARY OF THE INVENTION The object of the invention is to provide an alloy steel having a relatively low manganese content and, with the introduction of other alloying elements in relatively small percentages, provide an alloy composition which will have abrasion resistance and impact resistance which is equal to or superior to that of the high-alloy, high-manganese alloy steels of the prior art.

Another object of the invention is to provide an abrasion resistant alloy steel of the character described which will work harden for improved Wear characteristics in field use.

Still another object of the invention is to provide a low-manganese alloy steel Which, when heat treated in a particular manner, will provide the desired characteristics above enumerated.

Another object of the invention is to provide an alloy steel having a relatively low overall alloy content, which will nevertheless provide superior abrasion resistance and impact resistance in field use.

Still another object of the invention is to provide a work-hardenable, abrasion-resistant alloy steel which is more economical in cost than the high alloy steels heretofore required for equivalent purposes.

Other objects and advantages of the invention will become apparent during the course of the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is directed to an alloy steel Whose dominant alloying element is manganese and which contains other alloying elements in lesser percentages. The

other alloying elements are nickel, molybdenum, silicon, copper and carbon.

The alloy of the invention contains more than 1.8 and less than 2.5% manganese; 0.70 to 1.25% nickel; 0.10 to 0.30% molybdenum; 0.05 to 0.50 copper; 0.15 to 0.30% silicon; 0.24 to 0.30% carbon; with the remainder being substantially all iron.

A melt of the alloy steel, containing the alloying elements within the ranges above specified, is permitted to solidify and is then heat treated by water quenching the alloy steel from a temperature of 1600-1700 F. and tempering the quenched alloy steel at 825-1040 F. This produces a tough, fine-grained structure having a Brinell hardness number of at least 300.

The nickel acts to modify and reduce the brittleness imparted by the manganese and also acts to provide improved impact resistance and toughness. Copper is introduced into the alloy primarily to enhance its corrosion resistance and, therefore, its proportion may be very small ordinarily, but should be increased within the limits set forth when it is known or anticipated that corrosive conditions will be encountered in the use of the alloy steel.

The above-defined composition of alloy steel has good tensile strength in the range of 165,000 to 220,000 p.s.i.; good yield strength in the range of 135,000 to 171,500 p.s.i.; and is adaptable to conventional welding and flame cutting processes. It has the unusual attribute of work-hardening in use to enhance the initial BHN value by at least 15%, so that its abrasion resistance is enhanced when the material is worked in the field. The work-hardened surface of a typical plate or Weldment is approximately 19, inch deep and this is the surface that has the superior wear and abrasion resistance. Below this surface, the original softer, tough core of alloy steel still remains to maintain the desired characteristic of improved impact resistance.

A representative melt of this alloy steel consists of 2.20% manganese, 0.70% nickel, 0.20% molybdenum, 0.10% copper, 0.25% silicon, and 0.29% carbon, with the remainder being substantially all iron. It will be noted that in this representative composition, iron constitutes in excess of 96% of the composition and all the other alloying elements combined constitute less than 4% of the composition.

The solidified melt of the foregoing composition is water quenched from 1660 F. under a platen and then tempered at 900 F. The surface hardness of the material gives a reading of 321 BHN using the standard Brinell hardness test. Uniform samples of the material, inch thick were subjected to shot blast for 200 hours and then showed an increase in hardness to 341 BHN. The same samples were again subjected to shot blast for an additional 300 hours. The samples were again tested for hardness and showed a surface hardness of 375 BHN which represents a 17% increase over the initial surface hardness of the rolled alloy steel as a consequence of the shot blast work hardnening. The shot blast technique produces results comparable to those achieved as a result of abrasion and impact in field use of the alloy steel.

It will be understood that to those skilled in the art, the duration and technique to be utilized in the quenching and tempering process can be established to achieve the desired results.

It will be apparent from the foregoing that I have provided a work-hardenable alloy steel having a relatively low manganese content and having a relatively low overall proportion of alloying elements to provide a high strength, tough, abrasion-resistant and impactresistant material at relatively low cost. The heat-treated alloy steel of the defined composition is suitable for use in essentially all applications which have heretofore relied upon the high-manganese alloy steels of the prior art.

Having thus described my invention, I claim:

1. A heat-treated alloy steel consisting of more than 1.8 and less than 2.5 percent manganese, 0.70 to 1.25 percent nickel, 0.10 to 0.30 percent molybdenum, 0.05 to 0.50 percent copper, 0.15 to 0.30 percent silicon, 0.24 to 0.30 percent carbon, and the remainder iron in excess of 96.0 percent of the entire composition, and characterized by an initial hardness of at least 300 BHN which is work-hardenable to increase the initial BHN by at least 15% to enhance its abrasion resistance in use.

2. A heat-treated alloy steel as defined in claim 1 containing 2.2 percent manganese, 0.70 percent nickel, 0.20 percent molybdenum, 0.10 percent copper, 0.25 percent silicon, and 0.29 percent carbon, and characterized by an initial hardness of at least 311 BHN which is workhardenable to at least 368 BHN.

3. The process of producing a work-hardenable abra- 20 References Cited UNITED STATES PATENTS Mitchell 75-125 X Finkl 75--125 Mickelson et a1. 148-36 Hamilton 75-123 N Bagsar 25128 R CHARLES N. LOVELL, Primary Examiner US. Cl. X.R. 

